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Year : 2019  |  Volume : 16  |  Issue : 4  |  Page : 138-143

Medication adherence and influencing factors in patients with type 2 diabetes attending a tertiary hospital in South-West Nigeria

Department of Clinical Pharmacy and Biopharmacy, Faculty of Pharmacy, University of Lagos, Lagos, Nigeria

Date of Web Publication22-Oct-2019

Correspondence Address:
Mrs. Ebele Eugenia Onwuchuluba
Department of Clinical Pharmacy and Biopharmacy, Faculty of Pharmacy, University of Lagos, Idi-Araba, Lagos
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jcls.jcls_40_19

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Background and Objectives: Adherence to antidiabetic medications represents a huge hurdle that needs to be overcome for patients to gain maximum clinical benefits from their therapies. Several factors have been associated with patient adherence. This study assessed adherence to antidiabetic medications and evaluated the influence of pill burden on adherence. Materials and Methods: This is a cross-sectional study of 418 consenting patients with established type 2 diabetes attending the endocrinology Outpatient Clinic of a Tertiary Hospital. Patients were approached consecutively and surveyed using a questionnaire comprising information on demographics, medication adherence, and factors affecting adherence. Data on medication regimen and comorbidities were extracted from participants' case records. The study lasted for 15 months. Data were analyzed and summarized using descriptive and inferential statistics. Results: Nearly 27.5% of the participants were adjudged nonadherent to antidiabetic medications. The average number of antidiabetics was 1.56 ± 0.617. Of the number of participants that are adherent, nearly 33% and 35% of them were on one and two antidiabetic medications, respectively. However, been on three or more medications is associated with poorer adherence. Participants on metformin had better adherence compared to those on insulin alone or insulin plus oral antidiabetics. Short duration of diabetes (P = 0.048), older age (P = 0.024), and high educational level (P = 0.002) are associated with better adherence. Conclusion: A substantial number of patients were non-adherent to their antidiabetic medications. Been prescribed 3 or more antidiabetic medications was associated with poor adherence. The association between adherence to medication and glycemic control is not significant. High Pill-burden, young age, low educational level are potential targets for interventions.

Keywords: Adherence, antidiabetic medications, glycemic control, Nigeria, type 2 diabetes

How to cite this article:
Onwuchuluba EE, Soremekun RO, Oyetunde OO. Medication adherence and influencing factors in patients with type 2 diabetes attending a tertiary hospital in South-West Nigeria. J Clin Sci 2019;16:138-43

How to cite this URL:
Onwuchuluba EE, Soremekun RO, Oyetunde OO. Medication adherence and influencing factors in patients with type 2 diabetes attending a tertiary hospital in South-West Nigeria. J Clin Sci [serial online] 2019 [cited 2020 Aug 10];16:138-43. Available from: http://www.jcsjournal.org/text.asp?2019/16/4/138/269719

  Introduction Top

Medications are recommended strategies for the treatment of hyperglycemia. Past decades have recorded tremendous advances in the development and manufacturing of highly potent and efficacious medications, yet achieving good glycemic control has remained elusive. This is attributed to nonadherence (NA) to prescribed medications and other self-care.[1],[2] The burden of NA is high. NA has been associated with poor clinical outcomes, poor quality of life, early onset of complications, high rates of hospitalization, high health-care cost, and premature death,[3],[4] and has remained a clinical hurdle for patients, health system, and health-care providers.[1],[5],[6] NA is a hidden problem that has existed from antiquity (200 DC) till date [7] and when inaccurately identified, it has led to incorrectly adjudging a therapy ineffective, unnecessary therapy escalations and switches, ordering of expensive diagnostic tests, and disease progression.

Adherence is the extent to which a person's behavior, in terms of taking medication, following a diet plan and exercise, coincides with medical or health advice.[8] NA to medications can occur at any stage along the medication-taking continuum, during the initiation of therapy and implementation or discontinuation of the prescribed regimen,[9] and can be primary or secondary in nature.[10] Factors impacting adherence can be patient related (low health literacy, poor knowledge of disease and medication, and beliefs), health system related, disease related, prescriber related (communication barriers and multiple prescribing), and medication related (complex medication regimens and high pill burden).[11],[12],[13]

Studies have shown variations in the levels of adherence to medication regimen globally. A systemic review identified adherence to oral hypoglycemic medications in patients with type 2 diabetes to vary between 36% and 93% and to insulin at 63%.[13] An earlier study had revealed that about 50% of chronically ill patients in developed nations do not take their medication as prescribed.[11]

Recent studies have shown wider variations in adherence rates. While a study in Malaysia reported a 53% NA rate among patients with type 2 diabetes,[14] in Ethiopia, a NA rate of 25.4% was noted.[15] In Nigeria, NA varied between 25% and 70%.[16],[17],[18],[19] However, inconsistencies and variations on the exact influence of these factors on adherence need further investigation.

The effect of number of antidiabetic medications on adherence and glycemic control has been sparsely investigated in this locale. Hence, in the face of the rising prevalence of type 2 diabetes in a developing nation where health resources and facilities are scarce, better understanding of the influence of these factors could enhance prescribing practices, conserve resources, and assist in targeted interventions. This study assessed the levels of patients' adherence to antidiabetic medications and evaluated the influence of number of antidiabetic medications on adherence and glycemic control.

  Materials and Methods Top

The study was carried out at the endocrinology outpatient clinic of a tertiary health-care hospital in Lagos. The hospital is a 700-bedded hospital located at a suburban area of Mushin local government area of Lagos and offers comprehensive specialist care to both staff and diabetes patients on referral from other private, primary, and secondary health facilities. Ethical approval to conduct this study was obtained from the Health Research and Ethics Committee of Lagos University Teaching Hospital. Research instrument was coded for anonymity, and study was done at no cost to the participants.

A cross-sectional, self-administered questionnaire survey was conducted on 418 participants with type 2 diabetes mellitus, aged 18 years and older, on at least one antidiabetic medication for at least 6 months, and attending the endocrinology outpatient clinic of the hospital for follow-ups. Participants were approached consecutively and recruited if eligible and fulfilling the inclusion criteria. Newly diagnosed patients not on any antidiabetics and the seriously ill were excluded from the study. Written informed consent was obtained from the participants after the study aims and procedure were explained. The sample size was determined using the single-population proportion formula based on the following assumptions: the prevalence of NA to oral hypoglycemic medications was taken as 40% from a previous study.[19] The desired degree of precision was 5% and 95% confidence interval. Using a contingency of 10% for nonrespondents gave a final sample size of 406 which was made up to 418 for good representation. Data were collected using a 20-item multidimensional questionnaire comprising demographics such as disease duration, age, marital status, ethnicity, religion, level of education, employment status, average income, medication regimen, comorbidities (nine items); types of medication-taking behaviors (three items); and factors affecting medication adherence (6 items) and adherence using 2-item medication use domain of the Summary of Diabetes Self-Care Activities-Revised,[20] – a reliable scale and has been used in similar population.[20],[21] It measures the percentage of participants that took their antidiabetic medications in a specified number of days in the previous 7 days. Responses ranged from 0 to 7 days, with a score of <3 considered as nonadherent, whereas a score of ≥3 considered as adherent. The study instrument was pilot tested, giving a Cronbach's alpha of 0.705. Analysis of variance was used to test the significant variation on the participants' rating of the items in the instruments. The results suggested that there is no variation on the rating of the items at F-values 81.067, 3.679, and 10.392 (P < 0.05). It took participants who could fill out the questionnaire themselves between 8 and 10 min and about 10 and 20 min for those who required assistance. Participants' records were simultaneously reviewed to validate information previously collected. The participants' fasting blood glucose measured in the clinic was documented, while their glycated hemoglobin (HbA1c) was measured in the clinic using a point-of-care SD A1cCare Test system. Fasting blood sugar (FBS) >130 mg/dl was considered poor and FBS 70–130 mg was considered good, whereas HbA1c >7% was classified as poor control and HbA1c <7% as good control.

Data analysis

Data generated were entered into Statistical Package for the Social Sciences software version 23 (SPSS Inc., Chicago, IL, USA). The sociodemographic characteristics of the study participants were described using frequencies and percentages, whereas normally distributed continuous variables such as duration of diabetes and HbA1c were presented as mean (±standard deviation). Pearson's Chi-squared test was used to determine the association between categorical variables such as gender, educational status, marital status, and adherence to medication. Student's t-test was used to determine the association between continuous variables such as age (normally distributed) and adherence. The level of statistical significance was set at 5%.

  Results Top

A total of 418 out of 460 patients approached (245 females and 173 males) took part in the study, giving a response rate of 90.1%. [Table 1] shows the mean age of participants as 58.3 ± 11.99 years, 78% were married, 44% had postsecondary education, 83.5% had type 2 diabetes for 19 years, and 97% had no health insurance. Most participants (72.5%) were adjudged adherent to their antidiabetic medications. The proportion of female participants adherent to their antidiabetic medications was more than their male counterparts but not statistically significant. Shorter duration of diabetes (P = 0.048), older age (P = 0.024), and higher educational level (P = 0.002) were associated with better adherence to medications.
Table 1: Association between patients' demographic characteristics and medication adherence

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Compared to the use of insulin alone (7%), majority of the participants (80%) were on oral antidiabetic medications alone with metformin (79.9%), which was the most frequently prescribed [Figure 1]. Taking prescribed antidiabetic medications at incorrect times (50.8%) was the most frequently observed NA behavior among the participants. Almost half (49.8%) of them often fail to buy medications immediately when they are exhausted [Figure 2].
Figure 1: Types of antidiabetes Medications used by Participants

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Figure 2: Distribution of participants according to their nonadherence behaviors

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The study participants were on an average of 1.56 ± 0.617 antidiabetic medications [Table 2]. Adherence is significantly influenced by the number of antidiabetic medications (P = 0.013), with those participants on one and two antidiabetic medications been more adherent compared to those participants on three antidiabetic medications [Table 2]. Most participants on one antidiabetic medication had better glycemic control compared to those on three medications although this difference was not statistically significant. Half of the participants (50.5%) had poor glycemic control [Table 2].
Table 2: Association between number of antidiabetic medications (pill burden) and adherence

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The study findings also revealed that there is no significant correlation between patients' medication adherence, FBS, and HbA1c at r = 0.032, 0.014. Meanwhile, there is a statistically significant correlation between patients' FBS and HbA1c at r = 0.327 (P < 0.05) [Table 3].
Table 3: Correlation between medication adherence and glycemic control

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Factors affecting adherence to antidiabetic medications were determined. High cost of medications, nonavailability or out of stock (o/s) of antidiabetics, and long waiting time at the pharmacy were the barriers to adherence in 85%, 64%, and 60% of the participants, respectively [Table 4].
Table 4: Factors affecting adherence to antidiabetic medications

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  Discussion Top

This study revealed that most of the participants were adjudged adherent to antidiabetic medications, which is comparable to other studies that documented high adherence levels of 75.4%, 72.5%, and 83.3% among patients.[17],[19],[21] Other studies reported low adherence to medications.[14],[22] These variations in the estimate of adherence between studies may be attributed to the lack of a standardized method of assessing adherence, patient populations, and differences in adherence cutoff points.[23] Participants' demographic characteristics, including short duration of diabetes, older age, and high educational status, were associated with better adherence to antidiabetic medications in this study, which has been reported elsewhere.[22] Participants who had diabetes for 19 years and lower had better adherence to medications compared to those with longer duration. This could be attributed to a decline in autonomy and motivation in engaging in self-care such as taking medications as the illness progresses. Self-management can be frustrating and overwhelming. Been older (≥60 years) was found to be associated with better adherence compared to a younger age. An Australian study which reported that patients >60 years were likely to be adherent compared to their younger counterparts collaborated these findings. This could be because young people are still economically active with numerous social concerns, compared to older ones who may have retired and have family members offering assistance in their diabetes care. Mastery of skill and awareness of the demands of diabetes as one advance in age could be another factor. The World Health Organization has long identified younger age as a factor associated with NA.[11] However, a study reported no association between young age and poor adherence.[15] Education is known to improve knowledge, self-efficacy, and confidence in managing many chronic illnesses including diabetes; good knowledge may not always translate to positive behavioral change. In this study, compared to participants with no formal education, those with postsecondary education were more adherent.

Most participants had no health insurance to cater for their medications; hence, out-of-pocket payment was predominant. This obviously has some financial implications in a developing economy like Nigeria where most people live below US$1/day. A study had documented that most patients pay for treatment and noted that health-care system in Nigeria is grossly inadequate to cater for the complexity associated with diabetes mellitus.[24] Although health insurance currently exists locally, awareness and uptake are still very low and as patients are confronted with the burden of cost, tough decisions are frequently made either to forgo paying for medications or attend to other social demands and vice versa. Hence, considerations of medication subsidy are vital.

Compared to insulin use only, most participants were on oral anti-diabetics and had better adherence. A similar trend was observed in Malaysia where most patients were not on insulin therapy [22] but differs from a study done in Ethiopia where majority of the participants (47%) were on insulin.[25] The low insulin use may be attributed to cost, patients' perceptions about insulin, and clinical inertia by clinicians in prescribing insulin. Clinical inertia is the delay to initiate or intensify therapy when clinically indicated,[26] which could have contributed partially to the less-than-optimal glycemic control observed in this study. Initiation of insulin therapy once oral antidiabetics have failed in controlling glucose after intensifications of oral treatment has long been emphasized by past and current treatment guidelines.[3],[27] Patients are often reluctant to accept insulin because they view insulin as a measure of the seriousness of diabetes.[28]

Been on 1 or 2 antidiabetic medications was associated with better adherence compared to been on ≥3 antidiabetic medications. However, a study reported that patients on 4 or more medications had better adherence compared to those on <4 medications;[29] other studies found no association between the number of medication and adherence.[14] High pill burden could impact adherence to medication.

Initiation, implementation, and discontinuation of therapy are the three components of medication-taking behaviors.[9] Hence, in this study, taking medication at incorrect times (50.8%) was common and represents an implementation problem. Consistent with this finding are studies that recorded dose omissions as NA behaviors.[1],[30] Poor execution of therapy from underdosing is associated with diminished or absence of drug action.

In this study, nonavailability/o/s of antidiabetic medications, cost of medications, lack of adequate information on medication use, lack of family support, and long waiting time at the pharmacy are barriers to adherence and are in line with other studies.[18],[30] Provision of written instructions by pharmacists could assist patients in remembering to take their medication.

The present study findings also revealed that family support influenced adherence negatively. Hence, family members should be actively involved and adequately educated on their relevance in diabetes management. They should be trained to serve as cues or reminders for medication taking. Tying medication taking to daily activity and setting off alarm clocks are other positive measures.

Most participants were adjudged adherent although a substantial number of participants were nonadherent. Less than half of the participants had good glycemic control (HbA1c <7%), but no significant association existed between HbA1c and adherence. This, however, underscores the effectiveness of adherence in multiple domains of medication taking, diet, and exercise in controlling glycemia. Although this study provided valuable information on adherence to antidiabetic medications and factors that could affect adherence in a resource-constrained setting, it has some limitations. The inclusion of one tertiary health institution limits the generalization of the findings. Self-report assessment of adherence is prone to recall bias and social desirability as patients often want not to be seen as defaulters, yet it remains the most convenient, easy-to-administer, and the most cost-effective method in most clinical settings.

  Conclusion Top

A substantial number of participants were not adherent to their anti-diabetic medications, been prescribed 3 or more antidiabetic medications was associated with poor adherence. The association between adherence to medication and glycemic control was not significant. Hence, adherence in multiple domains of medication-taking, exercise, healthy diet, self- monitoring of glucose is essential for optimal glycemic control. Younger age, shorter duration of diabetes, and lack of family support were associated with poor adherence and are potential targets for interventions. Pharmacist should assume strategic roles in diabetes management. Further exploration of the role of family support in the management of Type 2 diabetes is crucial.

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Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Figure 1], [Figure 2]

  [Table 1], [Table 2], [Table 3], [Table 4]


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